Abstract
1. A high immediate mortality rate of released animals is an important cause of translocation failure (release cost). Post-release dispersal (i.e. the movements from the release site to the first breeding site) has recently been identified as another source of local translocation failure. In spite of their potential effects on conservation program outcomes, little is known about the quantitative effects of these two sources of translocation failure and their interactions with environmental factors and management designs. 2. Based on long-term monitoring data of captive-bred North African houbara bustards (hereafter, houbaras) over large spatial scales, we investigated the relative effects of release (e.g., release group size, period of release), individual (e.g., sex and body condition) and meteorological (e.g., temperature and rainfall) conditions on post-release survival (N = 957 houbaras) and dispersal (N = 436 houbaras). 3. We found that (i) rainfall and ambient air temperature had respectively a negative and a positive effect on houbara post-release dispersal distance, (ii) in interaction with the release period, harsh meteorological conditions had negative impact on the survival of houbaras, (iii) density dependent processes influenced the pattern of departure from the release site and (iv) post-release dispersal distance was male-biased, as natal dispersal of wild birds (although the dispersal patterns and movements may be influenced by different processes in captive-bred and in wild birds). 4. Synthesis and applications. Overall, our results demonstrate that post-release dispersal and mortality costs in translocated species may be mediated by meteorological factors, which in turn can be buffered by the release method. As the consequences of translocation programs on population dynamics depend primarily upon release costs and colonisation process, we suggest that their potential interactions with meteorological conditions be carefully addressed in future programs.